No abstract

This study examines the possible effect of the record ice jam of 1984 in the St. Clair River on river bed changes and conveyance. Numerical simulations were made to examine the flow and bed shear stresses during the jam formation and release periods. Simulation results indicate that the ice jam in the river did not cause a significant increase in bed shear stress compared to pre-and post-jam open water conditions. The insignificant change on bed shear stress during the ice jam period is the result of the large flow depth and the limited jam thickness. The bed shear stresses are much less than the critical shear stress for bed particle movement. This implies that the jam may not have had a significant impact on the channel conveyance.Résumé : La présente étude examine les effets possibles des embâcles observés en 1984 sur la rivière Sainte-Claire sur les modifications du lit du cours d'eau et sur l'écoulement de ce dernier. Des simulations numériques ont été réalisées pour étudier le débit et les contraintes de cisaillement exercées sur le lit de la rivière lors les périodes de formation d'embâcles et pendant les débâcles de glaces. Ces simulations montrent que les embâcles de la rivière n'entraînaient pas d'augmentation significative des contraintes de cisaillement exercées sur le lit du cours d'eau, si l'on compare ces dernières à celles enregistrées dans la rivière avant et après la formation des embâcles. Les très faibles variations de contrainte de cisaillement observées dans le lit durant la formation des embâcles s'expliquent par la profondeur importante de la rivière et par la faible épaisseur de la glace au niveau des embâcles. Les contraintes de cisaillement exercées sur le lit sont bien inférieures aux contraintes de cisaillement limites liées au mouvement des particules du lit. De ce fait, les embâcles pourraient ne pas avoir d'impact significatif sur l'écoulement du cours d'eau. [Traduit par la Rédaction]Mots-clés : érosion de lit, embâcle, modélisation mathématique, dynamique de la glace de rivière, rivière Sainte-Claire.

Ice processes in general, and ice jams in particular, play a dominant role in the hydrologic regime of Canadian rivers, often causing extreme floods and affecting the life cycle of many aquatic, terrestrial, and avian species. Various numerical models have been developed to help simulate the formation and consequences of these very dynamic and often destructive jam events. To test and compare the performance of existing models, a series of three tests have been devised and coordinated by a task force appointed by the Committee on River Ice Processes and the Environment (CRIPE). The results indicate that the overall performance of the models is good when calibration data are available, but considerably more varied when the models are applied in uncalibrated or “blind” mode. However, the diversity of results in the blind mode may be attributed more to the variations in perceptions of the physical processes by the users, as compared to the mechanics of the numerical computations.

A poorly designed culvert inlet structure causes scouring, which can lead to the collapse of the culvert and significant damage to the neighboring land. A set of laboratory tests was evaluated to examine velocity distribution at the culvert inlet. A three-dimensional acoustic Doppler velocimeter was used to measure instantaneous flow velocity upstream of the culvert. The analysis of mean velocities, turbulence strength, and Reynolds stresses was performed to understand the flow structure near the culvert entrance.

In the Vistula Lagoon, storm surges are induced by variable sea levels in the Gulf of Gdańsk and wind action. The rising of the water level in the southern part of the basin, exceeding 1.0 m above mean sea level, can be dangerous for the lowland area of Żuławy Elbląskie, causing the inundation of the polders adjacent to the lagoon. One of the potential possibilities to limit the flood risk is to decrease the water level in the lagoon during strong storm surges by opening an artificial canal to join the lagoon with the Gulf of Gdańsk. The decision to build a new strait in the Vistula Spit was made in 2017. In order to analyze the impact of the artificial connection between the sea and the lagoon during periods of high water stages in the southern part the lagoon, mathematical modelling of the hydrodynamics of the Vistula Lagoon is required. This paper presents the shallow water equations (SWEs) model adapted to simulate storm surges driven by the wind and sea tides, and the numerical results obtained for the present (without the new strait) and future (with the new strait) configuration of the Vistula Lagoon.